Hitherto, in carrying out motion prediction of an interlaced moving picture comprised of sets of groups of pixels (generally called picture blocks or macro blocks) consisting of a plurality of pixel data, in the case where, e.g., moving pictures of two frames of a frame picture serving as a current picture (current frame picture) A and a frame picture serving as a reference picture (reference frame picture) B are used to calculate motion vector MV.sub.AB from the current frame picture A to the reference frame picture B, there is a method of accumulating or cumulatively calculating, by the number of pixels within corresponding picture block, absolute values (or square values, etc. ) of differences between respective correspondence pictures of picture blocks of the both frame pictures to obtain predictive error value E (x, y) to select an optimum (ordinarily, minimum error) candidate vector from a plurality of candidate vectors mv(x,y) corresponding to respective picture blocks within a search range given in advance to employ it as the motion vector MV.sub.AB.
Namely, in the case of determining motion vectors of an interlaced picture by using such a motion vector detecting system, there is adopted a system in which data of both pictures of current frame picture A and reference frame picture B are merely inputted to a circuit for calculating motion vectors to obtain, at this circuit, error quantity outputs corresponding to respective candidate vectors of candidate vector groups (candidate vector groups corresponding to respective picture blocks within the search area) which are considered as candidate to employ a candidate vector corresponding to the error quantity output which is minimum among them as motion vector MV.sub.AB of that picture (picture block).
Meanwhile, in the so-called MPEG2, adaptive switching between motion compensated prediction of the frame base and motion compensated prediction of the field base is allowed. In the case of carrying out such adaptive switching, in macro block of P picture, for example, the following five motion predictive error calculations are required.
Namely, when it is assumed that odd field of current frame picture A is current odd field ao, even field thereof is current even field ae, odd field of reference frame picture B to be searched is reference odd field bo, and even field thereof is reference even field be, five motion predictive error calculations of calculation of motion vector MV.sub.AB from current frame picture A to reference frame picture B, calculation of motion vector MV.sub.aobo from current odd field ao to reference odd field bo, calculation of motion vector MV.sub.aobe from current odd field ao to reference even field be, calculation of motion vector MV.sub.aebo from current even field ae to reference odd field bo, and calculation MV.sub.aebe from current even field ae to reference even field be are required.
It is general to carry out, in parallel, these five motion predictive error calculations by using five hardware of similar structure for respectively carrying out corresponding calculations. Accordingly, large-scale of equipment constitutes problem.